These are not solid proof of illegal driving and police are often reluctant to carry out time consuming blood tests.

The breakthrough means officers would be able to identify drugs by taking a swab from a driver's mouth.

They would then place the sample into a machine and the result would be returned just five minutes later.

Drugs are considered a contributing factor is three percent of death on British roads - but this is likely to be underestimated due to the difficulty in detecting substances.

A spokesman for Universal Sensors Ltd said police did often not go on to test for drugs in drink drivers as the procedure was so time consuming.

''Drugs and alcohol are often consumed simultaneously, but once the police have detected alcohol they are unlikely to go to the effort of drug testing," he said.

''The VantixTM biosensor has the potential to provide police with a straightforward, unambiguous test result, which would help identify drug drivers and secure convictions.

''Such a sensitive technology would make a zero tolerance approach to drug drivers possible for the first time."

He added: "'A test which can be performed on untreated saliva by a member of the police force would save police time and resources, and increase the proportion of drug driver convictions, making the roads safer for all.''